﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.IO;

namespace MedicalCare.Common
{
    public class FileDownload
    {
        public HttpResponse Response = null;

        public FileDownload(HttpResponse response) {
            Response = response;
        }

        /// <summary>
        /// TransmitFile实现下载
        /// </summary>
        /// <param name="path"></param>
        public void FileDownLoadByTransmit(string filePath)
        {

            Response.ContentType = "application/x-zip-compressed";
            Response.AddHeader("Content-Disposition", "attachment;filename=z.zip");
            string filename = System.Web.HttpContext.Current.Server.MapPath(filePath);
            Response.TransmitFile(filename);
        }

        /// <summary>
        /// //WriteFile实现下载
        /// </summary>
        /// <param name="filePath"></param>
        public void FileDownloadByWriteFile(string filePath)
        {
            FileInfo fileInfo = new FileInfo(filePath);
            Response.Clear();
            Response.ClearContent();
            Response.ClearHeaders();
            Response.AddHeader("Content-Disposition", "attachment;filename=" + filePath);
            Response.AddHeader("Content-Length", fileInfo.Length.ToString());
            Response.AddHeader("Content-Transfer-Encoding", "binary");
            Response.ContentType = "application/octet-stream";
            Response.ContentEncoding = System.Text.Encoding.GetEncoding("gb2312");
            Response.WriteFile(fileInfo.FullName);
            Response.Flush();
            Response.End();
        }

        /// <summary>
        /// //WriteFile分块下载
        /// </summary>
        /// <param name="filePath"></param>
        /// <param name="chunkSize"></param>
        public void FileDownloadByWriteFile(string filePath, long chunkSize)
        {
            System.IO.FileInfo fileInfo = new System.IO.FileInfo(filePath);

            if (fileInfo.Exists == true)
            {
                long ChunkSize = chunkSize;//100K 每次读取文件，只读取100K，这样可以缓解服务器的压力
                byte[] buffer = new byte[ChunkSize];

                Response.Clear();
                System.IO.FileStream iStream = System.IO.File.OpenRead(filePath);
                long dataLengthToRead = iStream.Length;//获取下载的文件总大小
                Response.ContentType = "application/octet-stream";
                Response.AddHeader("Content-Disposition", "attachment; filename=" + HttpUtility.UrlEncode(fileInfo.Name));
                while (dataLengthToRead > 0 && Response.IsClientConnected)
                {
                    int lengthRead = iStream.Read(buffer, 0, Convert.ToInt32(ChunkSize));//读取的大小
                    Response.OutputStream.Write(buffer, 0, lengthRead);
                    Response.Flush();
                    dataLengthToRead = dataLengthToRead - lengthRead;
                }
                Response.Close();
            }
        }

        //流方式下载
        public void FileDownloadByStream(string filePath)
        {
            //以字符流的形式下载文件
            FileStream fs = new FileStream(filePath, FileMode.Open);
            byte[] bytes = new byte[(int)fs.Length];
            fs.Read(bytes, 0, bytes.Length);
            fs.Close();
            Response.ContentType = "application/octet-stream";
            //通知浏览器下载文件而不是打开
            Response.AddHeader("Content-Disposition", "attachment;  filename=" + HttpUtility.UrlEncode(fs.Name, System.Text.Encoding.UTF8));
            Response.BinaryWrite(bytes);
            Response.Flush();
            Response.End();

        }

    }
}